1. Field of the Invention
The present invention relates to a beam irradiation apparatus and a beam irradiation method.
2. Description of the Related Art
In a semiconductor production process, an ion implantation process that is implanting ions to a semiconductor wafer is generally performed for the purpose of changing the conductivity of the semiconductor and/or the crystalline structure of the semiconductor. An apparatus that is used in the ion implantation process is called an ion implantation apparatus, and has a function of generating ions by ionization in an ion source and a function of forming an ion beam by acceleration and a function of transporting the ion beam to an implantation processing chamber and irradiating a wafer inside the processing chamber with the ion beam. The ion implantation apparatus is an example of abeam irradiation apparatus which is used to irradiate a processed object with a charged particle beam configured by charged particles such as ions or electrons.
An index representing a state of convergence or divergence of a charged particle beam with respect to a traveling direction is called “Emittance”. For example, the emittance is provided by x−θ distribution in which a position x in a plane perpendicular to a beam trajectory and an angle θ between a traveling direction of charged particles at the position x and the beam trajectory are plotted on an x−θ plane. For example, an ion beam is limited by a small hole and emission of light generated by incidence of the beam passing through the small hole on a fluorescent screen is measured by an image sensor, so that an incident angle or emittance of the ion beam is measured.
When the angle of the ion beam incident on the wafer is changed, the form of interaction between the ion beam and the wafer is changed, which is known to affect processing results of the ion implantation. Accordingly, in order to appropriately control the ion implantation process, it is required to comprehend angle information of the ion beam. In certain, in order to evaluate quality of the ion implantation process with respect to the entire wafer, it is important to know how much ion irradiation is performed on each point of the wafer at individual incident angles. In other words, instead of measuring angle information on the ion beam with which the wafer is irradiated, when seen from a point on the wafer, measurement of angle information on ions incident into the point is required.